$(document).ready(function () {
    var list = $('#list_news');
    $('.nav li').hover(function (event) {
        var e = event || e;
        e.stopPropagation();
        e.preventDefault();
        $(this).find('.u-snav').stop().toggle();
    });
    $('.serve .item').hover(function () {
        $(this).find('.z-show').toggleClass('show');
    });

    var num = 0;
    var wHeight = window.screen.availHeight;
    var top_div = document.getElementById("top_div");
    window.onscroll = function () {
        var bHeight = $('body').height();
        var t = document.documentElement.scrollTop || document.body.scrollTop;
        if (t >= 300) {
            top_div.style.display = "inline";
        } else {
            top_div.style.display = "none";
        }

    };

    $("#top_div").click(function () {
        document.body.scrollTop = 0;
        document.documentElement.scrollTop = 0;
    });

});
